Scala 2.13 - implementing Non-Blocking Calls in Futures and Thread Pool Saturation
I've been struggling with this for a few days now and could really use some help. I've looked through the documentation and I'm still confused about I've been struggling with this for a few days now and could really use some help. I'm relatively new to this, so bear with me. I'm working with a question with using `Future`s in Scala 2.13 where my application seems to be hitting a thread pool saturation scenario. I've set up a non-blocking system using `scala.concurrent.Future` and `ExecutionContext`, but I'm seeing unexpected delays and timeouts in my application. Specifically, when I run a batch job that spawns multiple futures to process a list of URLs, the application becomes unresponsive, and I receive the following behavior: `java.util.concurrent.RejectedExecutionException: Task java.util.concurrent.FutureTask@... rejected from java.util.concurrent.ThreadPoolExecutor@...`. I believe this is related to my thread pool configuration. Here's a simplified version of my code where I initiate the futures: ```scala import scala.concurrent.{Future, ExecutionContext} import scala.util.{Success, Failure} implicit val ec: ExecutionContext = ExecutionContext.fromExecutorService(java.util.concurrent.Executors.newFixedThreadPool(10)) val urls = List("http://example.com/1", "http://example.com/2", "http://example.com/3") val futures: List[Future[Unit]] = urls.map { url => Future { // Simulate a blocking call to fetch the URL println(s"Fetching $url") Thread.sleep(2000) // Simulating a blocking operation } } Future.sequence(futures).onComplete { case result => result match { case Success(_) => println("All URLs fetched successfully") case Failure(e) => println(s"Failed with exception: ${e.getMessage}") } } ``` In this code, I've intentionally added a `Thread.sleep(2000)` to simulate a blocking operation. However, I'm not sure if the fixed thread pool is the right choice for handling concurrent tasks like this. Should I increase the number of threads, or is there a more efficient approach I should consider? I've also read about using `async`/`await` patterns in Scala, but I'm not clear on how that would change my current approach. Any advice would be greatly appreciated! What am I doing wrong? This is part of a larger application I'm building. The stack includes Scala and several other technologies. Thanks for taking the time to read this!